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Biomedical subjects

J E Haddow

Publications and source records attributed to J E Haddow.

At least 19 recordsLinked to original sources
PubMed2003

Iodine sufficiency and measurements of thyroid function in maternal hypothyroidism.

OBJECTIVES: To test the hypothesis that thyroglobulin (Tg) and free T4 (FT4) concentrations more than 2SD from the control mean are not increased in pregnancy in an iodine replete area in the absence of elevated TSH concentrations. The second hypothesis to be tested was that if such abnormalities in FT4 and Tg in the absence of elevated TSH concentrations were to exist they would not be associated with lowered IQs in the progeny. DESIGN: Cross-sectional study in New England comparing TSH, Tg, antibodies to Tg and FT4 in volunteer nonpregnant women 20-40 years old with those in hypothyroid mothers and matched euthyroid control mothers. The results are contrasted with those from similar studies reported from iodine deficient areas. SUBJECTS: Sera obtained at 17 weeks gestation and stored at -20 degrees C for 8 years were retrieved and analysed from 62 mothers with subclinical hypothyroidism and 124 matched euthyroid mothers. The diagnosis of hypothyroidism was made by finding a TSH concentration > 97.7 percentiile for 25 000 consecutive pregnant women. Sera were also analysed from 53 healthy nonpregnant volunteer women aged 20-40 years. MEASUREMENTS: TSH, Tg and Tg antibodies were measured in the sera of the nonpregnant volunteers, and Tg and Tg antibodies in the sera of the pregnant women who had previously been analysed for TSH and FT4. The incidence of FT4 concentrations below the 2.3 percentile of nonpregnant laboratory controls was compared for the euthyroid and hypothyroid mothers and the laboratory normal controls. RESULTS: Thirty-one per cent of the 62 hypothyroid mothers had FT4 concentrations below the 2.3 percentile compared with only one (0.8%) of the euthyroid mothers. Mean Tg concentrations did not differ between the nonpregnant controls and the euthyroid pregnant women, 14 +/- 10 vs. 16 +/- 10 micro g/l. Tg concentration in the hypothyroid mothers was 44 +/- 61, significantly greater than for either of the euthyroid control groups, P < 0.005. Positive antibodies to Tg were found in 9% and 10% of the control groups and 57% of the hypothyroid mothers, P < 0.0005. When TSH is included as an independent variable in multiple linear and logistic regressions, FT4 and Tg no longer correlate significantly with IQs. CONCLUSIONS: The incidences of FT4 concentrations more than 2SD below the control mean and of Tg > 2SD above the control mean are significantly increased in hypothyroid mothers in iodlne-sufficient New England. However, in the absence of elevated TSH concentrations, the incidences of such abnormalities in FT4 and TG are negligible. Indeed, concentrations for FT4, Tg and Tg antibodies for nonpregnant and pregnant controls in our iodine-replete area do not differ significantly from each other or from previously reported normative concentrations with the methods used. Thus, pregnancy in New England neither increases Tg nor lowers FT4 concentrations.

Adult↗
PubMed2002

Assigning risk for Smith-Lemli-Opitz syndrome as part of 2nd trimester screening for Down's syndrome.

OBJECTIVES: To design a reliable model in the context of prenatal screening for assigning the risk in an individual pregnancy of Smith-Lemli-Opitz syndrome (SLOS) and assess its performance. SETTING: A 2nd trimester screening programme for Down's syndrome that measures unconjugated estriol (uE3) along with other serum markers. METHODS: Development of individual risk estimates with a trivariate model incorporating measurements of maternal serum uE3, alpha-fetoprotein (AFP), and human chorionic gonadotropin (hCG) in both SLOS and unaffected pregnancies. RESULTS: Population parameters were computed for the three analytes, as were pairwise correlation coefficients and truncation limits, based on an unbiased collection of 29 affected pregnancies. Published parameters were used for unaffected pregnancies. With a cut off level of risk of 1:50, 62% of SLOS pregnancies can be detected by initially identifying 0.34% of unaffected pregnancies as screen positive. About 1 in 90 screen positive pregnancies will be affected. CONCLUSIONS: It is possible to screen for SLOS as an add on to existing 2nd trimester maternal serum screening, if uE3 is already being measured. A large, prospective trial is necessary to determine whether diagnostic testing can be performed in maternal urine or serum rather than amniotic fluid.

Biomarkers↗
PubMed2001

Relation of severity of maternal hypothyroidism to cognitive development of offspring.

BACKGROUND: An association between maternal subclinical hypothyroidism and low intelligence quotient (IQ) in the offspring has recently been shown. OBJECTIVE: To provide evidence for the causality of the association by testing the hypothesis that severity of maternal hypothyroidism correlates inversely with IQ of the offspring. METHODS: IQ scores were compared among 8 year old offspring of 124 control mothers whose thyroid stimulating hormone (TSH) concentrations were < 98th percentile of a cohort of 25,000 mothers at 17 weeks gestation, of 28 untreated hypothyroid women whose TSH was between the 98th and 99.85th percentiles, and of 20 untreated women whose TSH concentration was > or = 99.85th percentile. RESULTS: Mean (SD) IQs for each group of children (in ascending order of maternal TSH concentration) were 107 (13), 102 (15), and 97 (14). The difference between the extremes was significant (p = 0.003). The percentage of children with IQs > 1 SD below the control mean was 15, 21, and 50 respectively (p = 0.003). The odds ratio of having an IQ > 1 SD below the control mean, after controlling for socioeconomic status, was 4.7 (p = 0.006) for the third group compared with the controls. CONCLUSIONS: The inverse correlation between severity of maternal hypothyroidism and IQ of the offspring supports a causal relation and makes the need to screen for and treat pregnant women for hypothyroidism even more compelling.

Case-Control Studies↗
PubMed2001

Clinical validation of a new dimeric inhibin-A assay suitable for second trimester Down's syndrome screening.

OBJECTIVE: To compare the Down's syndrome screening performance of a simplified dimeric inhibin-A assay (Diagnostic Systems Laboratories (DSL)) with an assay whose clinical utility has been established (Serotec). SETTING: A case control set consisting of 51 Down's syndrome and 245 matched unaffected pregnancies collected as part of an earlier multicentre cohort study. METHODS: Sera were assayed for dimeric inhibin-A using the DSL assay and Serotec reference assay. Data analysis included a method comparison of mass values, fit of data to a logarithmic Gausian distribution, and determination of detection and false positive rates. In addition, 234 fresh sera were assayed using the simplified method. RESULTS: The two assays showed a high correlation (r = 0.93) but average concentrations of the DSL assay were 48% higher. However, the differences were basically proportional over the range of values important for screening. The detection rate was essentially equivalent for the DSL assay whether analysed univariately or in combination with other markers (for example, 79% v 75% at a 5% false positive rate for the DSL and Serotec assays for the combination of alpha fetoprotein, unconjugated oestriol, human chorionic gonadotrophin, and dimeric inhibin-A, respectively). The 234 dimeric inhibin-A values measured on fresh sera fitted a logarithm Gaussian distribution for the DSL assay, as indicated by the fit to a probability plot. CONCLUSIONS: The Down's syndrome screening performance of a simplified dimeric inhibin-A immunoassay was equivalent to a more labour intensive established dimeric inhibin-A assay.

Adult↗
PubMed2001

Long QT syndrome in children: the value of rate corrected QT interval and DNA analysis as screening tests in the general population.

OBJECTIVE: To evaluate two hypothetical screening strategies for identifying children with long QT syndrome (LQTS), a cause of sudden death in childhood. METHODS: Families with KVLQT1, HERG, or SCN5A genotypes provided electrocardiographic (ECG) data for this analysis. This is the first time such genotype-phenotype information has been available. Using the LQTS genotype, the distributions of QTc in affected and unaffected children were established and screening performance for various QTc cut off points were modelled. The detection rate for DNA mutation analysis was determined from published experience. RESULTS: The mean QTc (SD) was 0.484 seconds (0.031) in 117 affected children and 0.420 seconds (0.021) in 133 unaffected children. A QTc cut off of 0.50 seconds in a population of 1 million children would identify 61 of the 200 affected children, and 100 unaffected children. Estimates of testing costs for a screening programme in the newborn period would be $327 869/case detected and $2 222 000/death avoided. Although not presently available for routine use, DNA analysis could, theoretically, identify 100 of the 200 children with LQTS within the same population, along with an estimated 100 unaffected children. CONCLUSION: The only available screening test for LQTS is ECG measurement. If DNA technology becomes available for screening, unit costs must be very low to be competitive. There are multiple problems with screening for LQTS: only a minority of children will be detected, cost/death avoided is high, and pilot studies would need to be in place for 5-10 years to document efficacy.

Adolescent↗
PubMed2001

Long QT syndrome in children: the value of the rate corrected QT interval in children who present with fainting.

OBJECTIVE: A strategy was evaluated for identifying a proportion of children with long QT syndrome (LQTS) using the rate corrected QT interval (QTc) to systematically evaluate children who faint. METHODS: QTc measurements and rates of fainting for the present analysis are available from families with KVLQT1, HERG, or SCN5A genotypes. QTc distributions in affected and unaffected children were documented and detection and false positive rates were modelled. RESULTS: The mean QTc (SD) in 117 affected children was 0.484 seconds (0.031), and 0.420 seconds (0.021) among 133 unaffected children. At a cut off of 0.49 seconds, QTc measurement will identify 42.5% of affected and 0.1% of unaffected persons with a history of fainting who are alive at the time of testing. Assumptions include a prevalence of 1:5000 for LQTS, 2% mortality with the first arrhythmia, and a rate of fainting of 50% in affected children and 7% in unaffected children. Given these variables, a QTc cut off of 0.49 seconds detects 42 of 200 affected, along with 70 unaffected children out of a population of 1 million. If QTc > or = 0.49 seconds is found in either parent of children with a QTc of 0.44 through 0.48 seconds, another 21 affected and 25 unaffected children will be identified. CONCLUSION: Systematically performing QTc measurements as part of the evaluation of children who faint might optimally identify about one third of patients with LQTS with few false positives and thereby offer an opportunity to prevent some sudden deaths.

Adolescent↗
PubMed2000

Maternal thyroid deficiency and pregnancy complications: implications for population screening.

OBJECTIVE: To examine the relation between certain pregnancy complications and thyroid stimulating hormone (TSH) measurements in a cohort of pregnant women. METHODS: TSH was measured in sera obtained from women during the second trimester as part of routine prenatal care. Information was then collected about vaginal bleeding, premature delivery, low birthweight, abruptio placentae, pregnancy induced hypertension, need for cesarean section, low Apgar scores, and fetal and neonatal death. RESULTS: Among 9403 women with singleton pregnancies, TSH measurements were 6 mU/l or greater in 209 (2.2%). The rate of fetal death was significantly higher in those pregnancies (3.8%) than in the women with TSH less than 6 mU/l (0.9%, odds ratio 4.4, 95% confidence interval 1.9-9.5). Other pregnancy complications did not occur more frequently. CONCLUSION: From the second trimester onward, the major adverse obstetrical outcome associated with raised TSH in the general population is an increased rate of fetal death. If thyroid replacement treatment avoided this problem this would be another reason to consider population screening.

Adult↗
PubMed1999

Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child.

BACKGROUND: When thyroid deficiency occurs simultaneously in a pregnant woman and her fetus, the child's neuropsychological development is adversely affected. Whether developmental problems occur when only the mother has hypothyroidism during pregnancy is not known. METHODS: In 1996 and 1997, we measured thyrotropin in stored serum samples collected from 25,216 pregnant women between January 1987 and March 1990. We then located 47 women with serum thyrotropin concentrations at or above the 99.7th percentile of the values for all the pregnant women, 15 women with values between the 98th and 99.6th percentiles, inclusive, in combination with low thyroxine levels, and 124 matched women with normal values. Their seven-to-nine-year-old children, none of whom had hypothyroidism as newborns, underwent 15 tests relating to intelligence, attention, language, reading ability, school performance, and visual-motor performance. RESULTS: The children of the 62 women with high serum thyrotropin concentrations performed slightly less well on all 15 tests. Their full-scale IQ scores on the Wechsler Intelligence Scale for Children, third edition, averaged 4 points lower than those of the children of the 124 matched control women (P= 0.06); 15 percent had scores of 85 or less, as compared with 5 percent of the matched control children. Of the 62 women with thyroid deficiency, 48 were not treated for the condition during the pregnancy under study. The full-scale IQ scores of their children averaged 7 points lower than those of the 124 matched control children (P=0.005); 19 percent had scores of 85 or less. Eleven years after the pregnancy under study, 64 percent of the untreated women and 4 percent of the matched control women had confirmed hypothyroidism. CONCLUSIONS: Undiagnosed hypothyroidism in pregnant women may adversely affect their fetuses; therefore, screening for thyroid deficiency during pregnancy may be warranted.

Adult↗
PubMed1999

Antepartum fetal and maternal carboxyhemoglobin and cotinine levels among cigarette smokers.

The objective of this study was to examine the association of carboxyhemoglobin (COHb) and plasma cotinine levels among pregnant women who smoke cigarettes and their fetuses. Fifteen pregnant women who smoked and their fetuses undergoing cordocentesis had blood samples analysed simultaneously for COHb and cotinine. Linear regression was used to test for associations among study variables. Significant maternal-fetal associations were observed both with COHb (r = 0.72, p = 0.003) and with cotinine (r = 0.96, p = 0.003). Maternal cotinine levels were correlated with maternal and fetal COHb levels (r = 0.96, p = 0.003; r = 0.99, p = 0.0003, respectively). Fetal cotinine levels were correlated with COHb in maternal and in fetal blood (r = 0.81, p = 0.0003; r = 0.88, p<0.0001, respectively). The strong direct associations of maternal and fetal levels of COHb and cotinine indicate that maternal COHb and cotinine measurements may be interpreted as surrogates of fetal COHb levels. However, the specificity, ex vivo stability and ease of measurement of cotinine offer advantages over using COHb in quantifying fetal CO exposure following maternal cigarette smoking.

Adult↗
PubMed1999

Issues in implementing prenatal screening for cystic fibrosis: results of a working conference.

OBJECTIVE: To summarise a conference convened to examine how cystic fibrosis screening might appropriately be introduced into routine prenatal practice. METHODS: Participants included experts from various relevant disciplines. Systematic reviews and data from individual trials were presented; issues were identified and discussed. RESULTS: Judged by published criteria, prenatal cystic fibrosis screening is suitable for introduction. Screening can be performed cost effectively by identifying racial/ethnic groups at sufficient risk and then using either of two models for delivering laboratory services. Validated educational materials exist. Ethical issues are not unique. CONCLUSIONS: Once adequate facilities for patient and provider education, testing, counselling, quality control, and monitoring are in place, individual programmes can begin prenatal screening for cystic fibrosis.

Clinical Trials as Topic↗